This invention relates to a hybrid-type device for inflating vehicle safety equipment with a gas chamber for acceptance of compressed gases and at least two charges for the production of gas.
Such hybrid-type inflating devices, in which the inflation of the corresponding device is achieved, for one thing by a pressurized gas, and for another by a gas produced by igniting a gas-producing pyrotechnic charge, is known for example, from U.S. Pat. No. 3,758,131 or DE-OS 23 00 577. The minimum of two gas-producing charges can be ignited independently or sequentially. In this manner, the inflation process can be adapted to various parameters such as, for example, the weight of the occupants, the distance of the occupants from the safety equipment, the temperature, the force of the impact and similar. A time delay between the actuation of the various charges causes a gentler but also longer-lasting inflation of the safety equipment.
With known hybrid type inflation devices, it was difficult, however, to ignite the charges precisely at the predetermined times and to achieve the desired inflation characteristics. For example, there was a risk that the second charge would ignite unintentionally, for example as a result of an electric arc or electric leakage or through a transfer of heat from the first gas charge ignited.
The interaction of the two charges is a particular problem when these gas charges are of larger sizes. On the other hand, it is desirable for larger charges to be used to achieve a corresponding volume of gas to inflate the safety equipment and to achieve the desired inflation characteristics.
Proposals have already been made to not use electric ignition to ignite the gas-producing charges, to avoid electric wires in the gas chamber and to prevent electric arcs or leakage losses. But this makes it difficult to activate the charges independently at times to be defined.
The present invention therefore relates to creating an improved inflation device of the type cited at the beginning that avoids the known disadvantages in the state of the art. In particular, an inflation device is created in which the gas-producing charges produce a sufficient quantity of gas and can be ignited simply, independently of each other, at different times.
According to the invention, this task is solved by an inflation device of the type cited at the beginning in that the two charges each have a mass of at least 5% of the mass of the compressed gas and are each arranged outside the gas chamber on different sides thereof
The charges are therefore distances from each other and separated from the compressed gas in the gas chamber. There is no direct interaction between the charges upon ignition. In particular, thermal transfer from the charge ignited first to the second charge is prevented. Despite this, the two charges are sufficiently large. In particular, they are dimensioned such that each charge can cause a significant rise in temperature of the compressed gas in the gas chamber to influence the inflation process thereby. The charges can be ignited simply with an electric ignition initiator with no fear of a disruptive discharge or leakage losses. In particular, the two charges can be positioned at opposite ends of the gas chamber.
According to an advantageous development of the invention, pyrotechnic charges are used that produce carbon monoxide or other combustible gases. To oxidize these gases, the compressed inert gas stored in the gas chamber can be mixed with approximately 10%-20% oxygen (O2). An advantageous inflation characteristic can thus be achieved by mixing the gases produced by the pyrotechnic charges with the compressed gas stored in the gas chamber.
The inflation device can work without material that are broken down, in particular, by pyrolysis and thus produce gas. The pyrotechnic charges are sufficiently large to produce the corresponding gas volumes by themselves. By mixing the gases produced by the pyrotechnic charges with the inert gas stored in the gas chamber, a substantial increase in the temperature of the inert gas can be achieved, to influence the inflation process accordingly.
According to a preferred embodiment of the invention, the gas chamber is formed essentially cylindrically and the charge is situated on the face opposite thereto. This prevents an undesirable reciprocal impact from the ignitable gas charges.
On the first side of the gas chamber, on which the first of the charges is situated, a gas chamber opening is preferably provided that leads to the safety equipment and is initially sealed with a corresponding seal. The compressed gas is therefore completely separated from the charges.
In a development of the invention, the charges are contained in separate charge chambers that each have a charge chamber opening. These charge chamber openings are initially sealed with corresponding seals. Expediently, each of the charges can be brought into a flow connection with the gas chamber and the compressed gas stored therein. This can be arranged by opening the corresponding openings, i.e., the gas chamber openings and/or the charge chamber openings.
Various methods can be provided to open the seals for the gas chamber opening and/or the charge chamber openings. For example, they can be activated from outside. According to a preferred embodiment of the invention, however, the seals are self-controlled, i.e., they are designed to be activated by the resultant gas pressure after ignition of the charges. Preferably, the seals for the gas chamber opening are designed such that they are opened by the expanding gas after ignition of any one of the charges. By ignition of at least one of the two charges, the resultant charge gas flows through and the compressed gas stored in the gas chamber flows out. The seals for the charge chamber opening are designed such that they are opened exclusively by the related charge, i.e., by the expanding gas after ignition of the corresponding charge. The ignition of the other charge preferably does not impact the seal for the other charge chamber.
In a development of the invention, to open the seal for the gas chamber opening, i.e., the opening through which the compressed gas in the gas chamber can exit, a piston can be provided that, in its initial state, sits in a related cylinder and that is impinged upon by the expanding gas from one of the charges after ignition thereof, and this, in such manner that the piston is moved through the gas chamber opening. Here the piston opens the seal that had initially kept the gas chamber opening closed. Expediently, the piston can be impinged upon by one of the gas-producing charges situated on the side of the gas chamber opening.
According to a preferred embodiment of the invention, the piston-cylinder device has a plug that is assigned to the charge, that is situated in the corresponding charge chamber opening and that seals the same, fluid-tight, in its initial state. If the gas-producing charge situated in the corresponding charge chamber is ignited, the resultant gas pressure in the charge chamber acts on the plug through the opening of the gas chamber, releases it from the charge chamber opening and drives it through the gas chamber opening. The seals on the gas chamber opening are thus opened.
The seals for the gas chamber opening preferably have a sealing washer made of a suitable matter, that is fitted over the gas chamber opening and covers it. The contact pressure that activates the seal is preferably applied by the gas pressure inside the gas chamber; the sealing washer is pressured into the gas chamber wall by the compressed gas, into which wall the gas chamber opening is built. In a development of the invention, the seals on the piston are supported, and the central section of the sealing washer can lie on the ends of the plug sealing the charge chamber opening.
An advantageous embodiment of the invention consists in the piston being situated, in its initial position, such that the cross-section of the gas chamber opening is reduced and, in its extended position, it frees the cross-section of the gas chamber opening. Various discharge speeds can be achieved for the gas exiting from the gas chamber. In the initial piston position, the gas chamber openingxe2x80x94with the seals openxe2x80x94has an annular cross-section that is enlarged when the piston is removed.
Preferably, the piston can lie with its end in the plane of the gas chamber opening. In particular, the head section of the piston has a larger diameter than that of the related cylinder and a smaller diameter that the gas chamber opening. The above-cited achievement of varying opening cross-sections for the gas chamber opening facilitates this.
In a development of the invention, the gases exiting the gas chamber do not expand directly into the safety equipment. A joint discharge chamber can be provided that can be brought into flow connection with the gas chamber as well as the charge chambers, directly or indirectly. All exiting gases first expand in the discharge chamber and from it through a discharge opening into the safety equipment.
Advantageously, the discharge chamber is located between the gas chambers and one of the discharge chambers and can be brought into flow connection with both of these, directly; in particular, the discharge chamber is situated coaxially to the longitudinal axis of the gas chamber, like a sandwich between it and one discharge chamber. The other charge on the opposite side of the gas chamber can be brought indirectly into flow connection with the discharge chamber. The gas produced by this charge first flows through the corresponding charge chamber opening to the gas chambers, from them into the discharge chamber and from there into the safety equipment. The different connections of the various chambers to the discharge opening permits multi-faceted, precise adaptation of the inflation characteristics to the parameters mentioned at the beginning.
To achieve various inflation characteristics, the charges are preferably different. In particular, they are of different sizes, i.e., the gas volume produced upon ignition and the resultant pressure are different from the individual charges. The mass of the two charges can come to approximately 5% to 20% of the mass of the gas stored in the gas chamber, while preferably one of the charges has a mass of about 5%-10%, and the other charge has a mass of about 10%-20% of the mass of the compressed gas. Furthermore, the charges can be of different chemical compositions; in particular, they can have different ignition or expansion speeds.
To adapt the inflation characteristics to the corresponding environmental and accident parameters, according to an advantageous embodiment of the invention, a control device is provided to control the charges that predetermines the ignition sequences of the charges. The inflation device can therefore be operated accordingly in different inflation modes.
In a first inflation mode, only the first of the charges is ignited by the control device. The second charge is not ignited; the related charge chamber remains sealed. In a second inflation mode, the second charge is ignited, while the first is not. This means that the plug sealing the charge chamber opening belonging to the first charge remains in its initial position, so that the gases exiting from the gas chamber must flow through the cross-section of the gas chamber opening, reduced by the plug cross-section. In the first inflation mode, on the other hand, the plug is driven out so that a larger gas chamber opening section is available and the gas can exit correspondingly faster.
In a third inflation mode, the two charges are ignited. A larger volume of gas accordingly flows into the safety equipment. Preferably, the two charges are ignited sequentially with a time delay.